1. Technical Field
This relates generally to phase change memory devices.
2. Description of the Related Art
Phase change memory devices use phase change materials, i.e., materials that may be electrically switched between a generally amorphous and a generally crystalline state, for electronic memory application. One type of memory element utilizes a phase change material that may be, in one application, electrically switched between a structural state of generally amorphous and generally crystalline local order or between different detectable states of local order across the entire spectrum between completely amorphous and completely crystalline states. The state of the phase change materials is also non-volatile in that, when set in either a crystalline, semi-crystalline, amorphous, or semi-amorphous state representing a resistance value, that value is retained until changed by another programming event, as that value represents a phase or physical state of the material (e.g., crystalline or amorphous). The state is unaffected by removing electrical power.
Program performance is one of the key features of phase change memories. Buffer programming allows writing multiple data bytes (e.g. 64) at a time. In practice, buffered programming operations try to improve the programming performance by spreading the overhead time (e.g. for setup) over the entire buffer program time. Programming algorithms are normally implemented in assembly language, using an on-board code-execution processor and appropriate code portions.
However, a certain delay is inherent in executing the software for writing data. This delay arises because of the lines of code used, although in some cases relatively large groups of cells may be written at a time. Thus, several writing operations are repeatedly carried out to program an array of substantial size and increment of address and sequencing of the control signals can anyway incur a lot of overhead to the programming operation.